Adjustable resistance



S. EVERSHED.

ADJUSTABLE RESISTANCE.

Patented Jan. 3, 1922.

4 SHEETS SHEET 1.

INVENTOR ATTORNEY S. EVERSHED.

ADJUSTABLE RESISTANCE.

APPLICATION FILED APR. 22. I9I9.

1,402,587. ifii ed 3, 1922.

. HEETSSHEET 2.

S Eversfieal.

' BY aZ/QM ATTORNEY S. EVERSHED.

ADJUSTABLE-RESISTANCE.

PLlCA N FILED 1 ,402,587 Patented Jan. 3, 1922,

4 EEEEEEEEEEEE 3- .14 Y X Y S. EVERSHED.

ADJUSTABLE RESISTANCE.

APPLICATION FILED APR. 22, 1919.

Patented (12111.3, 1922.

4 4 SHEETSSHEET 4.

ATTORNEY UNITED STATES PATENT OFFICE.

SYDNEY EVER/SHED, OF LONDON, ENGLAND, ASSIGNOR OF ONE-HALF TO :EVERSHEDI AND VIGNOLES LIMITED, OF LONDON, GLAND.

ADJUSTABLE RESISTANCE.

Specification of Letters Patent.

Patented Jan. 3,1922.

Application filed April 22, 1919. Serial No. 291,978.

To all whom it may concern:

Be it known that I, SYDNEY EvERsHED, a subject of the King of GreatBritain and Ireland, and residing at Acton Lane Works, Chiswick, London,WV. 4., England, have invented certain new and useful Improvements inand Relating to Adjustable Resista'nces, of which the following is aspecification.

'The invention relates to adjustable resistances formed by winding aresistance wire in a spiral round an insulator support and in which theadjustment is eifected by relative sliding or rolling between the wireand a suitable contactor.

The objects of the invention are (1) to provide resistances, of the typedescribed, in the form of a ring in which the resistance" of, theconvolutions or turns of resistance wire is either accurately uniform orvaries accurately in any desired and prearranged manner around the ring;(2) to facilitate the construction of accurate lVheatstone bridges,potentiometers, and other socalled null method apparatus working on thesame or kindred principles, by means of a resistance of ring formadjustably divided into two or more portions by means of one or moreconductors in contact therewith and capable of relative motion thereon;(3) to facilitate the construction of apparatus for communicatinginformation from one place to another by means of resistance variationsin electric circuits on the principles described in British Patent No.8784 of 18-91.

The invention consists in a supporting ring adapted, by forming a gap orother discontinuity in it, to be interlinked with the mechanism of awire-winding machine; a uniform resistance wire Wound in a spiral aroundthe said ring iii accurately spaced convolutions; means for insulatingthe said resistance wire where required and one or more contactorsadapted by movements of relative rotation to'make contact with theresistance wire thereon at any desired angular position or positions.

The invention also consists in a supporting ring adapted, by forming agap or other discontinuity in it, to be interlinked with the mechanismof a wire-winding machine; a uniform resistance wire wound in a spiralround the said ring in accurately spaced convolutions; means forinsulating the said resistance wire where required and one or morecontact arms adapted to move about an axis normal to the plane of thering and to make contact with the resistance wire thereon at any desiredangular position' or pos tions.

The invention also consists in a supporting ring of insulating orinsulated material adapted by the shape of itscross section to giverigidlty in the plane of the ring; a gap in the ring adapted to permitit to be interlinked with the mechanism of a wire-winding machine; auniform resistance wire wound in a spiral round the said ring inaccurately spaced convolutions; means for insulating the said resistancewire where required and one or more contactors adapted to make contactwith the resistance wire on the periphery of the ring at any desiredangular position or positions.

The invention also consists in a supporting ring of insulating orinsulated material adapted by the shape of its crosssection to giverigidity in the plane of the ring; a gap in the ring adapted to permitit to be interlinked with the mechanism of a wire-winding machine;indentations in the ring adapted to receive and space the convolutionsof a resistance wire; a uniform resistance wire wound in a spiral roundthe said ring in the said indentations in accurately spacedconvolutions; and one or more contact arms adapted to move about an axisnormal to the plane of the ring and to make contact with the resistancewire thereon at any desired angular position or positions.

The invention also consist in a ring resistance in which the supportingring of insulating or insulated material is adapted by the shape of itscross section to give rigidity in the plane of the ring and furtheradapted, by the shape of its cross section to give such flexibility in adirection normal to the plane of the ring as will, in conjunction with anarrow gap or discontinuity in the same, permit theringtto beinterlinked with the mechanism of a wire-Winding machine for the purposeof winding the resistance wire in a spiral on the supporting ring.

Theinvention further consists in a sevcred resistance ring of the typedescribed,

in combination with a bond or other me- 'tations in the ring;

sistance ring to the original plane of the uncut supporting ring andfirmly securing 1t therein. v The invention is illustrated in theaccompanying drawings in which like letters refer to like parts.

In these drawings; .4 Figure 1 is a plan, and V I Figure 2 a sectionalelevation of one form of .ring resistance constructed according to thepresent invention in whic'hthe contactor takes the form of arolling'contact;

Figure 3 shows a modification in which a sliding contactor. is employedinstead of a rolling contactor;

Figures 4 and 5 illustrate convenient means which may be adopted forsecuring an accurate spacing of the convolutions of resistance wire bymeans of indentations;

Figure 6 shows one way of forming inden- Figures 7 and 8 illustrate aring of nearly square section substantially rigid in a direction normalto the plane of the ring and formed with a large gap;

Figure 9 and 10 represent a similar gapped ring of different crosssection;

Figures 11 and 12 show a ring sufiiciently thin to give flexibility inan axial direction and formed with a narrow gap;

Figures 13, 1 1, 15 and 16 show'me'a'ns of bonding the rings at the gap;

Figures 17 and 18 show rings in which the radialwidth increases from aminimum at one end to a maximum in the middle, and a minimum at one endto a maximum at the other end respectively.

Figure 19 illustrates a convenient form of machine for w1nd1ng the wireon to rings as described above.

In carrying the invention into effect in the form shown by way ofexample in Figures 1 and 2, the supporting ring r may either be made ofa suitable insulating material such as hard ebonite or the like, or ofmetal covered with a suitable insulating var- .nish or enamel. The ringhas. a gap at gr sufliciently wide to enable it to be interlinked with awinding machine for the purpose of winding on the spiral convolutiofisof resistance wire w. lhe adjust- I able or travelling contactor isshown by way lin of example as an elastic disc 0 which, being freelypivoted in one end, of the arm Z carried by the axle a, makes a rollingcontact with the resistance wire w. The other end of the arm Z makessliding contact with the slip ring a. The ends of the resistance wireare fastened toterminals 2? and t and a terminal t on the slip ringenables the necessary electrical connection with the travelcontactor 0to be made. In Figure 3 a s iding contactor 0 is shown as an'alternativeto therolling disc contactor shown in F1gures 1 and 2. The resistancewire is sulation on the wire may be removed throughout a narrow bandround the ring, to

enamel or other'suitable insulating material, and aftenthe winding iscompleted the inform a suitable path for the travelling contactor.

Figures 1 and 5 illustrate convenient means which can be adopted forsecuring accurate spacing of the convolutions of resistance wire w bymeans of indentations n n, in the supporting ring 1*.- In Figure 4 theindentations are in the form of shallow grooves on the inner and outerperipheries of the supporting ring. These grooves may be cut in anysuitable gear cutting machine.

In Figure 5 the indentations n n are merely notches formed in the edgesof the ring, a modification which permits them to be formed by squeezingthe supporting ring in a suitable press between rings of steel or otherhard metal upon which corresponding vteeth have been cut in a gearcutting machine. The operation of forming indentations in this way isillustrated byway of example in Figure 6, where r is the support.

ring interlinked with a winding machine.

The supporting ring r is fixed in a position concentric with theturntable l of the winding machine, by means of the adjustable anddetachablesu'pports 2, 2, and is interlinked with the windin drum 3which is driven by the motor 4. he stock of resistance wire 5 is woundonthe wire drum'6 and is carried therefrom one, thezring' 1* by means ofguide pulleys and}; winding arm which are fixed on the drum 3. Thewinding arm is omitted in the drawing in order to show the wire passingon to the ring 1' at'the'winding point e. The turntable l' is driven atany desired relative speed by means" of change wheels 8, 9 and 10 whichare geared to and driven by the motor 4. "A friction brake 7 applies thenecessary'tension to the resistance wire. When, in the course of therevolution of the turntable 1, a supporting'clamp 2 approaches the backof the winding drum 3 it is detached from the turntable and ring. and replaced in a position in front of the winding drum near the winding point6.

When the resistance wire is of sufficiently small diameter it is easilywound in tight and flat convolutions on a ring of rectangular crosssections, the tension being sulficient not only to bend the wire roundthe ring but to pull it tightly across the fiat sides of the ring. Whenthe wire is too large in diameter to permit this to be done without theuse of excessive tension, a modified form of supporting ring like thatshown in F igures 9 and 10 may berused with advantage,

7: the elliptical or oval section permitting a stout wire to bendclosely round the supporting ring by the application of a moderatetension.

When the supporting ring has a section which makes it substantiallyrigid in a di rection normal tothe plane of the ring, the gap 9 must beat least as wide as the axial width of the winding drum of the windingmachine. Such a ring is illustrated in Figures 7 and 8, the sectionshown being nearly square, and also in'Figures 9 and 10. On the otherhand, if the supporting ring is sufficiently thin to give it thenecessary flexibilty in an axial direction, as illustrated 3 0 inFigures 11 and 12, the gap may be re"- duced in width to that of asawcut, and the ring may be readily interlinked with a wind- ,ing'machineby pulling apart the two ends m and y as indicated by dotted'lines inFigure 11. Removal from the winding machine,

after winding on the resistance wire, is performed in the same manner;the flexibility not being appreciably altered by the presence of theconvolutions of wire. 7

After winding on the resistance wire the two ends of the supporting ringmay be fastened rigidly together by means of a bond 5, as shown inFigures 13, 14, 15 and 16. In Figures 13 and 14 the bond is suitable fora more or less rigid ring which has a wide gap, and consists of a metalpiece accurately machined to slide into and close the gap 9, where it isretained in position by means of screws which pass through the 5 ends my of the ring 1*. Figures 15 and 16 show a bond suitable for a flexiblering in which the gap consists of a narrow saw cut. In Figures 1 and 3the convolutions of y resistance wire have a uniform resistance per turnfrom one end of the resistances to the other because the radial width ofthe supporting ring is uniform. By making the supporting rings ofnon-uniform radial width the resistance wire wound thereon will have anon-uniform resistance per turn,

the variation of resistance per turn correspending with the variation inthe perimeter of the transverse section of the supporting ring.

an example of this modification,

Figure 17 shows a supporting ring in which the radial width is a minimumat the gap 9 and increases at a uniform rate from the ance per turn fromw to m and uniformly decreasing resistance per turn from m to 3 The axlea which carries the contact arm is concentric with the inner circularperimeter of the resistance ring. Figure 18 shows another modificationin which the radial width of the supporting ring increases uniformlyfrom a minimum at the end a: up to a maximum at the other end y. InFigures 17 and 18 both the inner and outer peripheries of the supportingring are circular and consequently the rates of increase of resistanceper turn are uniform.

If desired, the supporting ring may be constructed with a non-circularperiphery calculated to give any desired law of variation of width. Thusany desired law of variation of resistance per turn may readily beobtained. The constructions described and illustrated in the drawingsmay be modified in other ways without departing from the essence of theinvention.

It will be understood that in applying the invention for, the purpose ofcommunicating information from one place to another the resistancesconstructed in accordance with the invention may either be used to varythe ratio of currents in two circuits or they may be used as thevariable resistances of a system of circuits connected on the principleof a Wheatstone bridge, as described in British Patent No. 8784 of 1891.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is 1. An adjustable resistance comprising asupporting ring, resistance wire spirally wound thereon of which theturns are accurately disposed round the ring, a contactor and means foreffecting adjustment by relative movement between the wire and thecontactor whereby said movement will result in a predetermined variationin the resistance.

2. An adjustable resistance comprising a supporting ring having adiscontinuity therein adapting it to be interlinked with the mechanismof a wire-winding machine; a uniform resistance wire wound in a spiralround the said ring in accurately spaced convolutions; means forinsulating the said resistance wire where required and a contactoradapted by a movement of relative rotation to make contact with theresistance w1re thereon at any desired angular position.

3. An adjustable resistance comprising a would have a uniformlyincreasing resistsupporting ring adapted, having a gap or otherdiscontinuity in it adapting it, to be interlinked with the mechanism ofa wirewinding machine; a uniform resistance wire wound in a spiral roundthe said ring in accurately spaced convolutions; meansfor in sulatingthe said resistance wire-whererequired, and a contact arm adapted tomove about an axis normal to the plane of the ring and to make contactwith the resistance wire thereon at any desired angular position.

4. An adjustable resistance comprising a supporting ring adapted by theshape of its cross section to give rigidity in the Jplane of the ring; agap in the ring adapte" to permit it to be interlinked with a mechanismof a wire-winding machine; a uniform resistance wire wound in a spiralround the said ring in accurately spaced convolutions; means forinsulating the said resistance wire where required and a contactoradapted to make contact with the resistance wire on the periphery of thering at any desired angular position. 5. An adjustable resistancecomprising a supporting ring adapted by the shape of its crosssection\to give rigidity in the plane of the ring; a gap in the ringadapted to permit it to be interlinked with the mechanism ofawire-winding machine;'indentations in the ring adapted to receive andspace .the convolutions of a resistance wire; a uniform resistance wirewound in a spiral round the said ring in the said indentations inaccurately spaced convolutions; and a contact arm adapted to move aboutan axis normal to the plane of the ring and to make contact with theresistance wire thereon at any desired angular position. t

6. A ring resistance comprising a supporting ring adapted by the shapeof its cross section to give rigidity in the plane of the ring andfurther adapted, by-the shape of its cross section, to give suchflexibility'in a direction normal to the plane of the ring as will, inconjunction with a narrow gap or discontinuity in the same, permit thering to be interlinked with the mechanism of a wirewinding machine forthe purpose of winding the resistance wire in a spiral on the supportingring.

7. An adjustable resistance comprising a discontinuous supporting ring,flexible in an axial direction, resistance wire disposed thereon inaccurately separated convolutions and detachable means for securingrigidity of the aforesaid wound ring.

8. An adjustable resistance comprising a discontinuoussupporting'ring,'fiexible in an axial direction; resistance wiredisposed thereon inaccurately separated convolutions, a bond rigidlyattached to the discontinuous ring and bridging the discontinuity, acon- 65'tactor contacting with the resistance wire and means foreffecting adjustment of resist- "ance by relative movement between thewire and the contactor.

9. An adjustable resistance comprising a supporting ring adapted, byforming a gap or other discontinuity in it, to be interlinked with themechanism of a wire-winding machine; a uniform resistance wire wound ina spiral round the said ring in accurately spaced convolutions; meansfor insulating the said resistance wire where required, and contact-armsadapted to move about anaxis normal to the plane of tlie ring and tomake contact with the resistance wire thereon at any desired angularposition.

10. An adjustable resistance comprising a supporting ring, resistancewire thereon of which the resistance of the convolutions or turns isaccurately disposed round the ring, a plurality of contactors and meansfor effecting adjustment by relative movement between the wire and thecontactors.

11. An adjustable resistance comprising a supporting ring adapted, byforming a gap or other discontinuity in it, to be, interlinked with themechanism of a wire-winding machine; a uniform resistance wire wound ina spiral round the said ring in accurately spaced convolutions; meansfor insulating the said resistance wire where required, and a pluralityof contactors adapted by a movement of relative rotation ,to makecontact with-the resistance wire thereon at any desired angularposition. .7

' 12. In adjustable resistance comprising a 100 supporting ring adaptedby the shape of its cross section to give rigidity in the plane of thering; a gap in the ring adapted to permit it to be interlinked with themechanism of a wire-winding machine; a uniform re- .105-

adapted to 'make contactwith the resistance 1 wire on the periphery ofthe ring at any desired angular position.

13. An adjustable resistance colnpri'sin a supporting ring ofnon-uniform ra ial width,iresistance wire thereon of which theresistance ofthe convolutions or turns is accurately disposed roundthering, a contactor and means for effecting adjustment by relativemovement between the wire and the contactor.

14. An adjustable resistance comprising a supporting ring with anon-circular periphery, resistance wire thereon of which the resistanceof the convolutions or turns is accurately disposed round the ring, acontactor and means for effecting adjustment by relative movementbetween the wire and the contactor.

15. An adjustable resistance comprising a discontlnuous supporting ring,a uniform resistance wire wound in accurately separated turns aroundsaid ring and a contactor adapted by a movement of relative rotationbetween the wire and the contactor to make contact with the resistancewire thereon at any desired angular position. v

16. An adjustable resistance comprising a discontinuous supporting ring,a uniform resistance wire wound in accurately separated turns aroundsaid ring and a contact arm adapted to be moved about an axis normal tothe plane of the ring and to make contact with the resistance .wire. Intestimony whereof I have signed my name to this specification.

SYDNEY EVER-SHED.

